Given the tiny size of avian brains compare to mammals, particulary humans, it's hard to ascribe a lot of intelligence to them. But for what they can do, they seem quite well optimized.

Brain size is not a decisive factor in estimating intelligence and corvid brains pack twice the neurons per volume compared to humans. The factor is: effective "Information Processing Capacity" (IPC), which is high for body size and rivals great apes on specific executive tasks.

Extreme miniaturization eliminates travel distance, giving near-zero latency and high metabolic efficiency despite 1/5th the neurons of a chimp.

Bird brains are wired differently, neuron density is higher... so using size to compare brains is not enough.

https://www.scientificamerican.com/article/bird-brains-have-...

And that’s why Elephants are generally considered more intelligent than humans!